1. Field of Invention
The present invention relates to a method of brazing, and more particular to a method of ultrasonic brazing an aluminum alloy or aluminum matrix composite article with a base article.
2. Description of Related Arts
Aluminum and its alloy have the psychical properties of low-density, high strength and corrosion, and have a lower price compared to copper. The aluminum matrix composites also have the advantages of high strength, high modulus, heat resistance, corrosion resistance, abrasion resistance, good thermal conductivity of electrical conductivity, and small thermal expansion coefficient. Therefore, aluminum alloy and aluminum matrix composites are vital to the industries of aviation, aerospace, shipbuilding, automobiles, high-speed trains, and other fields. Generally, aluminum alloy and aluminum matrix composites are connected by brazing.
Traditionally, aluminum alloy is brazed in a vacuum environment. Accordingly, the brazing equipments are expensive and the working period thereof is relatively long. In addition, aluminum alloy cannot be brazed with complex constructions. In air, brazing of aluminum alloy needs fluxes to remove oxidized film, and help the liquid solder to wet the base material, which will unavoidably corrode the base material. Also, the melting point of the solder for traditional welding is high, and the brazing temperature is higher than 600° C. which is close to the critical point of the solid phase of the base material. Therefore, the brazing temperature needs to be accurately controlled within a narrowly temperature range such that the cost and time of the brazing operation will be significantly increased.
A filler metal for using in the welding operation is either a welding wire with particle filler or an alloy added filler metal, wherein the filler metal is reacted to generate a ceramic phase like reinforcement to reinforce the bond of the aluminum matrix composite. For example, the patents, U.S. Pat. No. 4,625,095 and U.S. Pat. No. 4,752,537, owned by Boeing Company provide a method that forms a fiber reinforced weld in a fiber reinforced metal matrix composite by both fibrous reinforcing material and powdered matrix metal or coating along the weld line prior to form the pool with mixture of adhesive, powdered matrix metal, and fibrous reinforcing material. U.S. Pat. No. 4,803,334, owned by Westinghouse Electric Corporation, provides a method that a substantially homogeneous metal matrix composite weld is formed by a laser beam welding while feeding a metal matrix composite filler wire into the weld pool. U.S. Pat. No. 4,738,389, owned by Moshier WC, teaches a method for welding metal composite materials, including metal-ceramic composites, whereby a weld or filler material is prepared by the in-situ precipitation of ceramic in a metallic matrix. The filler material may comprise boride, carbide, oxide, nitride, silicide, etc, while the matrix metal may constitute an alloy or intermetallic of two or more metals. China Pat No. CN1895830 from Jiang Su University teaches a method for plasma arc welding particle reinforced aluminum matrix composites by the in-situ precipitation of ceramic particle in weld. In the process, Ti, Zr, B, Si are added, wherein using the welding pool generated by the plasma arc welding, those elements are reacted with aluminum, nitrogen or reinforcement particles to form reinforcement, to prohibit harmful phase, and to realize the in-situ precipitation of the particles reinforced aluminum matrix composites welded joints. The research of University of Science and Technology Beijing teaches the mixture of Al powder, Si powder, SiC particles, or mixture of Al powder, Si powder, W particles as filling material to perform transient liquid phase diffusion bonding (Huang et al, Nonferrous Met. Soc. China. 2005, 15, 1067-1071). Harbin Institute of Technology discloses a method and a system for producing composite solder for particle reinforcement aluminum matrix composites brazing, and realized reinforced composite weld [China Pat No. CN1827809].